<!DOCTYPE html>
<html lang="zh-CN">
    <head>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <meta name="robots" content="noodp" />
        <meta http-equiv="X-UA-Compatible" content="IE=edge, chrome=1">
        <title>《Flutter文件下载器》 - 飞雪无情的博客</title><meta name="Description" content="专注于IT互联网，包括但不限于Go语言(golang)、Java、Android、Python、项目管理、抖音分析、软件架构等"><meta property="og:title" content="《Flutter文件下载器》" />
<meta property="og:description" content="
在这篇文章中，我们将构建一个简单的文件下载器，显示进度的视觉指示。
" />
<meta property="og:type" content="article" />
<meta property="og:url" content="https://www.flysnow.org/posts/flutter/flutter%E6%96%87%E4%BB%B6%E4%B8%8B%E8%BD%BD%E5%99%A8/" />
<meta property="article:published_time" content="2021-06-01T13:54:15+08:00" />
<meta property="article:modified_time" content="2021-06-01T13:54:15+08:00" />
<meta name="twitter:card" content="summary"/>
<meta name="twitter:title" content="《Flutter文件下载器》"/>
<meta name="twitter:description" content="
在这篇文章中，我们将构建一个简单的文件下载器，显示进度的视觉指示。
"/>
<meta name="application-name" content="飞雪无情的博客">
<meta name="apple-mobile-web-app-title" content="飞雪无情的博客"><link rel="shortcut icon" type="image/x-icon" href="/favicon.ico" />
        <link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png">
        <link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png"><link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png"><link rel="manifest" href="/site.webmanifest"><link rel="canonical" href="https://www.flysnow.org/posts/flutter/flutter%E6%96%87%E4%BB%B6%E4%B8%8B%E8%BD%BD%E5%99%A8/" /><link rel="prev" href="https://www.flysnow.org/posts/go/Go%E8%AF%AD%E8%A8%80%E6%9C%80%E4%BD%B3%E5%AE%9E%E8%B7%B5%E5%BB%BA%E8%AE%AE/" /><link rel="next" href="https://www.flysnow.org/posts/vscode%E5%BF%AB%E6%8D%B7%E9%94%AE%E5%A4%A7%E5%85%A8/" /><link rel="stylesheet" href="/lib/normalize/normalize.min.css"><link rel="stylesheet" href="/css/style.min.css"><link rel="stylesheet" href="/lib/fontawesome-free/all.min.css"><link rel="stylesheet" href="/lib/animate/animate.min.css"><script type="application/ld+json">
    {
        "@context": "http://schema.org",
        "@type": "BlogPosting",
        "headline": "《Flutter文件下载器》",
        "inLanguage": "zh-CN",
        "mainEntityOfPage": {
            "@type": "WebPage",
            "@id": "https:\/\/www.flysnow.org\/posts\/flutter\/flutter%E6%96%87%E4%BB%B6%E4%B8%8B%E8%BD%BD%E5%99%A8\/"
        },"genre": "posts","keywords": "flutter","wordcount":  291 ,
        "url": "https:\/\/www.flysnow.org\/posts\/flutter\/flutter%E6%96%87%E4%BB%B6%E4%B8%8B%E8%BD%BD%E5%99%A8\/","datePublished": "2021-06-01T13:54:15+08:00","dateModified": "2021-06-01T13:54:15+08:00","publisher": {
            "@type": "Organization",
            "name": "飞雪无情"},"author": {
                "@type": "Person",
                "name": "飞雪无情"
            },"description": ""
    }
    </script></head>
    <body header-desktop="" header-mobile=""><script type="text/javascript">(window.localStorage && localStorage.getItem('theme') ? localStorage.getItem('theme') === 'dark' : ('' === 'auto' ? window.matchMedia('(prefers-color-scheme: dark)').matches : '' === 'dark')) && document.body.setAttribute('theme', 'dark');</script>

        <div id="mask"></div><div class="wrapper"><div class="logo-wrapper">
  <a href="/%20/" class="logo">飞雪无情的博客</a>
</div>

<nav class="site-navbar">
  <ul id="menu" class="menu">
    <li class="menu-item">
      <a class="menu-item-link" href="/tools/">工具</a>
    </li><li class="menu-item">
      <a class="menu-item-link" href="/archives/">归档</a>
    </li><li class="menu-item">
      <a class="menu-item-link" href="/about/">关于</a>
    </li>
  </ul>
</nav><main class="main">
                <div class="container"><div class="toc" id="toc-auto">
            <h2 class="toc-title">Contents</h2>
            <div class="toc-content" id="toc-content-auto"></div>
        </div><article class="page single"><h1 class="single-title animated flipInX">《Flutter文件下载器》</h1><div class="post-meta">
            <div class="post-meta-line"><span class="post-author"><a href="/" title="Author" rel=" author" class="author"><i class="fas fa-user-circle fa-fw"></i>飞雪无情</a></span>&nbsp;<span class="post-category">included in <a href="/categories/Flutter/"><i class="far fa-folder fa-fw"></i>Flutter</a></span></div>
            <div class="post-meta-line"><i class="far fa-calendar-alt fa-fw"></i>&nbsp;<time datetime="2021-06-01">2021-06-01</time>&nbsp;<i class="fas fa-pencil-alt fa-fw"></i>&nbsp;291 words&nbsp;
                <i class="far fa-clock fa-fw"></i>&nbsp;One minute&nbsp;</div>
        </div><div class="featured-image"><img
        class="lazyload"
        src="/svg/loading.min.svg"
        data-src="https://luckly007.oss-cn-beijing.aliyuncs.com/img/90c6cc12-742e-4c9f-b318-b912f163b8d0.png"
        data-srcset="https://luckly007.oss-cn-beijing.aliyuncs.com/img/90c6cc12-742e-4c9f-b318-b912f163b8d0.png, https://luckly007.oss-cn-beijing.aliyuncs.com/img/90c6cc12-742e-4c9f-b318-b912f163b8d0.png 1.5x, https://luckly007.oss-cn-beijing.aliyuncs.com/img/90c6cc12-742e-4c9f-b318-b912f163b8d0.png 2x"
        data-sizes="auto"
        alt="https://luckly007.oss-cn-beijing.aliyuncs.com/img/90c6cc12-742e-4c9f-b318-b912f163b8d0.png"
        title="https://luckly007.oss-cn-beijing.aliyuncs.com/img/90c6cc12-742e-4c9f-b318-b912f163b8d0.png" /></div><div class="details toc" id="toc-static"  kept="">
                <div class="details-summary toc-title">
                    <span>Contents</span>
                    <span><i class="details-icon fas fa-angle-right"></i></span>
                </div>
                <div class="details-content toc-content" id="toc-content-static"><nav id="TableOfContents">
  <ul>
    <li><a href="#创建用户界面">创建用户界面</a></li>
  </ul>
</nav></div>
            </div><div class="content" id="content"><blockquote>
<p>在这篇文章中，我们将构建一个简单的文件下载器，显示进度的视觉指示。</p>
</blockquote>
<hr>
<h2 id="创建用户界面">创建用户界面</h2>
<div class="highlight"><div style="background-color:#fff;-moz-tab-size:4;-o-tab-size:4;tab-size:4">
<table style="border-spacing:0;padding:0;margin:0;border:0;width:auto;overflow:auto;display:block;"><tr><td style="vertical-align:top;padding:0;margin:0;border:0;">
<pre style="background-color:#fff;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f"> 1
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f"> 2
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f"> 3
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f"> 4
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f"> 5
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f"> 6
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f"> 7
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f"> 8
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f"> 9
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">10
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">11
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">12
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">13
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">14
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">15
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">16
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">17
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">18
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">19
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">20
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">21
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">22
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">23
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">24
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">25
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">26
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">27
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">28
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">29
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">30
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">31
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">32
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">33
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">34
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">35
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">36
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">37
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">38
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">39
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">40
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">41
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">42
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">43
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">44
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">45
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">46
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">47
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">48
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">49
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">50
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">51
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">52
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">53
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">54
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">55
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">56
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">57
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">58
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">59
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">60
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">61
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">62
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">63
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">64
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">65
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">66
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">67
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">68
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">69
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">70
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">71
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">72
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">73
</span><span style="margin-right:0.4em;padding:0 0.4em 0 0.4em;color:#7f7f7f">74
</span></code></pre></td>
<td style="vertical-align:top;padding:0;margin:0;border:0;;width:100%">
<pre style="background-color:#fff;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-dart" data-lang="dart"><span style="color:#000;font-weight:bold">class</span> <span style="color:#458;font-weight:bold">MyHomePage</span> <span style="color:#000;font-weight:bold">extends</span> StatefulWidget {
  <span style="color:#a61717;background-color:#e3d2d2">@</span>override
  _MyHomePageState createState() <span style="color:#000;font-weight:bold">=&gt;</span> _MyHomePageState();
}

<span style="color:#000;font-weight:bold">class</span> <span style="color:#458;font-weight:bold">_MyHomePageState</span> <span style="color:#000;font-weight:bold">extends</span> State<span style="color:#000;font-weight:bold">&lt;</span>MyHomePage<span style="color:#000;font-weight:bold">&gt;</span> {
  <span style="color:#000;font-weight:bold">var</span> downloading <span style="color:#000;font-weight:bold">=</span> <span style="color:#000;font-weight:bold">false</span>;
  <span style="color:#000;font-weight:bold">var</span> done <span style="color:#000;font-weight:bold">=</span> <span style="color:#000;font-weight:bold">false</span>;
  <span style="color:#458;font-weight:bold">double</span> progress;

  <span style="color:#a61717;background-color:#e3d2d2">@</span>override
  Widget build(BuildContext context) <span style="color:#000;font-weight:bold">=&gt;</span> Scaffold(
    <span style="color:#900;font-weight:bold">appBar:</span> AppBar(
      <span style="color:#900;font-weight:bold">backgroundColor:</span> Colors.transparent,
      <span style="color:#900;font-weight:bold">elevation:</span> <span style="color:#099">0</span>,
      <span style="color:#900;font-weight:bold">centerTitle:</span> <span style="color:#000;font-weight:bold">true</span>,
      <span style="color:#900;font-weight:bold">title:</span> Text(<span style="color:#d14">&#39;Downloader&#39;</span>),
      <span style="color:#900;font-weight:bold">actions:</span> [
        IconButton(
          <span style="color:#900;font-weight:bold">icon:</span> Icon(Icons.settings),
          <span style="color:#900;font-weight:bold">onPressed:</span> () {},
        )
      ],
    ),
    <span style="color:#900;font-weight:bold">body:</span> SizedBox.expand(<span style="color:#900;font-weight:bold">child:</span> Align(<span style="color:#900;font-weight:bold">child:</span> Column(
      <span style="color:#900;font-weight:bold">mainAxisAlignment:</span> MainAxisAlignment.center,
      <span style="color:#900;font-weight:bold">crossAxisAlignment:</span> CrossAxisAlignment.center,
      <span style="color:#900;font-weight:bold">children:</span> [
        <span style="color:#000;font-weight:bold">if</span> (downloading)
          SizedBox(
            <span style="color:#900;font-weight:bold">width:</span> <span style="color:#099">120</span>,
            <span style="color:#900;font-weight:bold">child:</span> LinearProgressIndicator(
              <span style="color:#900;font-weight:bold">value:</span> progress,
            ),
          )
        <span style="color:#000;font-weight:bold">else</span> <span style="color:#000;font-weight:bold">if</span> (done) ...[
          Image.network(<span style="color:#d14">&#39;https://i.tst.sh/XaY4i.jpg&#39;</span>),
          Padding(
            <span style="color:#900;font-weight:bold">padding:</span> EdgeInsets.all(<span style="color:#099">8</span>),
            <span style="color:#900;font-weight:bold">child:</span> RaisedButton(
              <span style="color:#900;font-weight:bold">child:</span> Text(<span style="color:#d14">&#39;Reset&#39;</span>),
              <span style="color:#900;font-weight:bold">onPressed:</span> () {
                setState(() {
                  done <span style="color:#000;font-weight:bold">=</span> <span style="color:#000;font-weight:bold">false</span>;
                });
              },
            ),
          )
        ] <span style="color:#000;font-weight:bold">else</span>
          RaisedButton(
            <span style="color:#900;font-weight:bold">child:</span> Text(<span style="color:#d14">&#39;Start&#39;</span>),
            <span style="color:#900;font-weight:bold">onPressed:</span> () <span style="color:#000;font-weight:bold">async</span> {
              setState(() {
                downloading <span style="color:#000;font-weight:bold">=</span> <span style="color:#000;font-weight:bold">true</span>;
                progress <span style="color:#000;font-weight:bold">=</span> <span style="color:#000;font-weight:bold">null</span>;
              });

              <span style="color:#000;font-weight:bold">for</span> (<span style="color:#458;font-weight:bold">int</span> i <span style="color:#000;font-weight:bold">=</span> <span style="color:#099">0</span>; i <span style="color:#000;font-weight:bold">&lt;=</span> <span style="color:#099">100</span>; i<span style="color:#000;font-weight:bold">++</span>) {
                setState(() {
                  progress <span style="color:#000;font-weight:bold">=</span> i <span style="color:#000;font-weight:bold">/</span> <span style="color:#099">100</span>;
                });
                <span style="color:#000;font-weight:bold">await</span> Future.delayed(Duration(<span style="color:#900;font-weight:bold">milliseconds:</span> <span style="color:#099">25</span>));
              }

              setState(() {
                downloading <span style="color:#000;font-weight:bold">=</span> <span style="color:#000;font-weight:bold">false</span>;
                done <span style="color:#000;font-weight:bold">=</span> <span style="color:#000;font-weight:bold">true</span>;
              });
            },
          ),
      ],
    ))),
  );
}
</code></pre></td></tr></table>
</div>
</div><p>这只是一个wireframe，实际上并不下载数据。</p></div><div class="post-footer" id="post-footer">
    <div class="post-info">
        <div class="post-info-line">
            <div class="post-info-mod">
                <span>Updated on 2021-06-01</span>
            </div>
            <div class="post-info-license"></div>
        </div>
        <div class="post-info-line">
            <div class="post-info-md"></div>
            <div class="post-info-share">
                <span></span>
            </div>
        </div>
    </div>

    <div class="post-info-more">
        <section class="post-tags"><i class="fas fa-tags fa-fw"></i>&nbsp;<a href="/tags/flutter/">flutter</a></section>
        <section>
            <span><a href="javascript:void(0);" onclick="window.history.back();">Back</a></span>&nbsp;|&nbsp;<span><a href="/">Home</a></span>
        </section>
    </div>

    <div class="post-nav"><a href="/posts/go/Go%E8%AF%AD%E8%A8%80%E6%9C%80%E4%BD%B3%E5%AE%9E%E8%B7%B5%E5%BB%BA%E8%AE%AE/" class="prev" rel="prev" title="《Go语言最佳实践建议》"><i class="fas fa-angle-left fa-fw"></i>《Go语言最佳实践建议》</a>
            <a href="/posts/vscode%E5%BF%AB%E6%8D%B7%E9%94%AE%E5%A4%A7%E5%85%A8/" class="next" rel="next" title="《Vscode快捷键大全》">《Vscode快捷键大全》<i class="fas fa-angle-right fa-fw"></i></a></div>
</div>
</article></div>
            </main><footer class="footer">
        <div class="footer-container"><div class="footer-line">Powered by <a href="https://gohugo.io/" target="_blank" rel="noopener noreffer" title="Hugo 0.79.1">Hugo</a> | Theme - <a href="https://github.com/dillonzq/LoveIt" target="_blank" rel="noopener noreffer" title="LoveIt 0.2.10"><i class="far fa-kiss-wink-heart fa-fw"></i> LoveIt</a>
                </div><div class="footer-line"><i class="far fa-copyright fa-fw"></i><span itemprop="copyrightYear">2021</span><span class="author" itemprop="copyrightHolder">&nbsp;<a href="/" target="_blank">飞雪无情</a></span></div>
        </div>
    </footer></div>

        <div id="fixed-buttons"><a href="#" id="back-to-top" class="fixed-button" title="Back to Top">
                <i class="fas fa-arrow-up fa-fw"></i>
            </a><a href="#" id="view-comments" class="fixed-button" title="View Comments">
                <i class="fas fa-comment fa-fw"></i>
            </a>
        </div><script type="text/javascript" src="/lib/smooth-scroll/smooth-scroll.min.js"></script><script type="text/javascript" src="/lib/lazysizes/lazysizes.min.js"></script><script type="text/javascript" src="/lib/clipboard/clipboard.min.js"></script><script type="text/javascript" src="/lib/sharer/sharer.min.js"></script><script type="text/javascript">window.config={"code":{"copyTitle":"Copy to clipboard","maxShownLines":10},"comment":{}};</script><script type="text/javascript" src="/js/theme.min.js"></script></body>
</html>
